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Comment by pessimizer | Hacker News Reader

Is there any evidence that synesthesia exists other than self-report?

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edit as a reply to both responses:

Tests like this were mentioned in the article - but wouldn't the same effect be caused by people who had an honest belief that they saw the number 8 as orange, or if you sat someone in a room and played a tape for an hour that "One. Blue. Two. Violet. Three. Green.[...]" etc.?

i.e. if I've said that I see 5 as blue enough times, wouldn't that affect my times on an association test?

Are there any stronger examples of tests? Any papers that I should read? Honest question; not trying to be contrarian.

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People who report synesthesia perform better at tasks such as counting 2's in a picture with 2's and 5's, owing to their different colours.

https://en.wikipedia.org/wiki/File:Synaesthesiatest.jpg

Yes, they've verified this in several ways, either test-retest (ask for a variety of synesthetic associations and verify them some time later) or even by constructing challenges that would be easier for synesthetes than non-synesthetes for example, detecting a shape in a mixed cloud of numbers based on associated hue (much like some color-blindness tests).

It is possible to observe how people react to things and infer a difference in perception. My oldest son likely has an auditory processing disorder and mishears things if he isn't watching someone talk. Other people will consistently agree that X was said while he insists it was Y.

When he was 19 and recovering from a health crisis, he casually mentioned that he knew he was getting better because heno longer tasted colors. I recently asked him what that meant and he said he perceived color but with his tongue.

They have developed vision products for blind people that feed data to the tongue to let them see. So, in some sense, new technology is confirming the ease with which we can cross wire the senses to perceive something typically only perceived by another sense.

The association tests that synesthete.org run don't use a grapheme -> categorized color task, but instead ask the user to visually select a color on a color map. This way, not only the reaction time, but the variance of selection can be observed. Also a bit surprised that the article mentioned nothing about Eagleman's research on this stuff.

Some recommended resources:

http://www.ncbi.nlm.nih.gov/pubmed/21923794

http://synesthete.org/

http://eaglemanlab.net/synesthesia

Are there any successful tests in which synesthetes mix colors accurately and quickly when numbers are placed near to each other? That would be impressive.

Daniel Tammet has some pretty impressive synaesthetic abilities. From Born on a Blue Day:

> I never write anything down when I'm calculating, because I've always been able to do the sums in my head and it's much easier for me to visualise the answer using my synaesthetic shapes than to try to follow the `carry the one' techniques taught in textbooks we are given at school. When multiplying, I see the two numbers as distinct shapes. This image changes and a third shape emerges --- the correct answer. The process takes a matter of seconds and happens spontaneously. It's like doing maths without having to think.

> [...] I'm multiplying 53 by 131. I see both numbers as a unique shape and locate each spatially opposite the other. The space created between the two shapes creates a third, which I perceive as a new number: 6943, the solution to the sum. [sic]

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